Load balancer for multiple subdomains with different IPs

What is the name of the domain?

example.com

What is the issue you’re encountering

Hello; I have two different systems on 2 different subdomains (say, a.example.com and b.example.com). a.example.com contains the IPs 10.0.0.1 and 10.0.0.2 (not real IPs), and b.example.com contains the IPs 10.0.0.3 and 10.0.0.4. Can I achieve that with a single $5 subscription, or would I need two of those, one for each subdomain?

The $5 plan comes with two origins. Your two more will be another $10 ($15 total per month).

I believe the two origin pools included would be enough for your two-subdomain setup.